Technical Field
The present disclosure relates to a liquid administration device.
Background Art
Conventionally, a prefilled syringe that is sterilely filled with a drug solution and can administer the drug solution has been known.
The prefilled syringe comprises a syringe outer cylinder which has an opening part through which the drug solution is discharged; a needle tube that is provided in the opening part of the syringe outer cylinder and has a sharp needle tip at a distal end of the needle tube; a gasket that is slidable in the syringe outer cylinder; a drug solution with which a space surrounded by the syringe outer cylinder and the gasket is filled; and a plunger which is interlocked with the gasket on a proximal side and discharges the drug solution through the opening part by pressing the gasket toward the distal direction. When administering the drug solution using the prefilled syringe, a living body is punctured with the needle tube, and the pressing operation of the plunger is performed in the punctured state. As a result, the drug solution is discharged from the opening part by the gasket. Accordingly, the drug solution can be administered to the living body through the needle tube.
However, the pressing operation of the plunger of the prefilled syringe can be performed at an arbitrary timing depending on a user. Therefore, there has been a concern that the pressing operation of the plunger may be erroneously performed before the living body is punctured with the needle tube. In this case, the drug solution unintentionally leaks from the needle tube, or in some cases, it is difficult to administer a sufficient amount of the drug solution to the living body since the drug solution is insufficient due to the leakage.
In order to prevent the above-described unintentional leakage of the drug solution from the needle tube, Japanese Patent No. 4287611 discloses a liquid administration device including a mechanism for inhibiting the pressing operation of the plunger using a coupling element. According to such a liquid administration device, when the pressing operation of the plunger is performed with force stronger than a predetermined threshold value, the coupling element moves in the distal direction and comes into contact with a predetermined part in the syringe outer cylinder. Accordingly, the state where the movement of the plunger is inhibited by the coupling element is released, and the plunger enters a state where the pressing operation of the plunger can be performed.
However, the liquid administration device disclosed in Japanese Patent No. 4287611 is configured such that the state where the movement of the plunger is inhibited by the coupling element is released by the coupling element moving in the axial direction. Therefore, there is a concern that the state where the movement of the plunger is inhibited by the coupling element cannot be maintained because the coupling element can move in the distal direction through the pressing operation of the plunger, even though it is unnecessary to move the plunger yet.